Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

515
FXUS63 KLOT 141138
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
538 AM CST Wed Jan 14 2026

.KEY MESSAGES...

- Turning sharply colder today behind a strong cold front early
  this morning with northerly winds gusting up to 30-40 mph.

- Wind-whipped snow showers likely this morning near and east of
  I-39, with lake enhancement commencing into northwest Indiana.

- Winter Weather Advisory remains in effect for northern and
  eastern Porter County for lake effect snow showers today and
  tonight, localized accumulations of 2-5 inches expected,
  especially northeast Porter County.

- A "Clipper Express" pattern may materialize from the end of
  this week into early next week with periodic opportunities
  for snow, reinforcing shots of cold air, and blustery
  northwest winds.

&&

.DISCUSSION...
Issued at 345 AM CST Wed Jan 14 2026

Through Thursday:

Temperatures have been running a few to several degrees milder
to this point than previously expected, but this will change
quickly as a strong cold front (over southern Wisconsin as of
this writing) sweeps southeastward across the area.

A potent vort lobe packing very cold mid-level temps can be seen
nicely on water vapor imagery this morning across north central
Wisconsin. It appears that the large scale forcing from the
vort lobe, along with sufficient frontal forcing, and sufficiently
deep convective cloud depths has been enough for a fairly well
organized area of snow showers extending across central
Wisconsin. These snow showers will push southward across areas
near and east of I-39 towards and after daybreak.

Bumped up PoPs to account for radar trends, and recent guidance
trends getting a much better handle on the snow showers this
morning. It doesn`t appear to be a high end snow squall
scenario, though we`ll need to watch for embedded "squall-like"
behavior with brief very low visibility and gusts perhaps a bit
higher than the already strong background wind fields expected
this morning. Air and pavement temps running above freezing
through the night may tend to limit pavement accumulations
unless under a more intense burst of snow. A bit more concern in
this regard for areas east of I-57 and particularly downwind of
Lake Michigan in northwest Indiana. A coating to locally a half
inch may occur on colder surfaces east of I-39 in Illinois, with
locally 1/2 inch to 1" in northwest Indiana, particularly in
Porter County due to north-northwesterly flow from the lake.

Also have been noting potential for some additional snow showers
to develop into northeastern and east central Illinois later
this morning in the strengthening cold air advection regime.
This may be tied to better deep layer moisture pivoting
southward catching up to the still strong large scale forcing.
All in all, any robust snow shower activity (outside of lake
effect snow in northwest Indiana), should be confined to
primarily this morning, ending early this afternoon near and
east of I-57 in eastern Illinois into Indiana well south of the
Kankakee River.

If temperatures fall quickly enough coincident with still
falling precipitation, there may be some potential for localized
"flash freeze" conditions, but it`s unclear how this will play
out. We`ll continue to monitor upstream observations, webcams,
and road conditions and may consider a Special Weather Statement
if warranted, in tandem with graphical messaging.

Temperatures will be in the low-mid 20s for most of the area
during the afternoon hours with north-northwesterly winds
continuing to gust up to 30-40 mph, strongest near the lake,
resulting in wind chills in the single digits for the evening
commute.

Castro

Regarding the lake effect snow...

There are no big changes in forecast thinking, with the Winter
Weather Advisory for Porter County starting at 8 AM and ending
Thursday morning. Will push out the advisory end time to 9 AM
Thursday, as light snow and blowing snow should extend into the
Thursday morning commute for northeastern sections of the
county.

Meteorologically, strong cold air advection over a fairly warm
lake (SSTs in the lower 40s over most of the open waters) should
result in moderately strong lake induced instability Wednesday
into Wednesday night. Inversion heights are progged to be
extreme, topping out 6-8kft, but plenty high to support some
heavy lake effect snow showers, particularly given the DGZ
embedded within the convective clouds.

Expecting mostly multi-banded lake effect set-up during the
daytime hours Wednesday, effecting northern and perhaps eastern
Porter County. Wednesday night, land breeze convergence could
lead to a more dominant, strong lake effect band, which would
likely take aim on areas east of Porter County. Some of the CAM
guidance suggests the there could be a weaker secondary band to
the west over Porter County or even just some weaker multi-band
structure snow showers. Lake effect chances for Porter County
look to decrease after sunrise Thursday morning as winds back
and push the band east into WFO IWX`s area. Given the strong
winds (at least minor blowing and drifting snow) and the
potential for 2-5" of snow, hazardous travel can be expected. As
is typically the case with lake effect, totals could vary
significantly over a short distance.

The rest of Thursday will be the temporary break before
accumulating snow arrives Thursday night, detailed in the next
section below. Highs will reach the mid to upper 20s.

Izzi/Castro

Thursday Night through Tuesday:

Global model guidance remains in good agreement in maintaining
a highly amplified upper level pattern, featuring a deep long-
wave trough across eastern North America, into early next week.
Several digging short waves are noted in EPS/GEFS and GEPS
ensembles through the period, with the first arriving Thursday
night. Spread decreases however, with the timing and track of
later successive disturbances. Overall, the pattern appears to
favor the potential for some accumulating snow Thursday night
into Friday with a bit a warm-up, followed by colder and
occasionally blustery weather punctuated by occasional periods
of snow/snow showers/flurries through the remainder of the
forecast period.

A mid-level short wave was evident in upper air data and GOES
vapor imagery off the British Columbia coast early this morning,
associated with a 150 kt upper level jet streak. This feature
is progged to cross the Canadian Rockies later tonight, then dig
southeast and amplify across the upper Midwest Thursday.
Increasing forcing for ascent develops ahead of the approaching
wave late Thursday/Thursday evening, resulting in top-down
saturation and the likely development of snow from west to east
across the area during the evening as a modest (~1004 mb)
surface wave develops along an occluding Pacific frontal trough.
Strongest forcing appears to persist through shortly after
daybreak Friday when the initial short wave vort and trough axis
passes. There are some lingering spatial differences in the
model QPF output with this wave, though with general agreement
in amounts around 0.15" liquid and Cobb snow/liquid ratios in
the 12-15:1 range. This would appear to support a snowfall in
the 1-3" or 2-3"range across the forecast area, though the
location of the higher amounts is of low confidence just yet.

While deep, synoptic ascent eases with the passage of the
initial wave Friday morning, continued deepening/amplification
of the upper level trough and associated cooling of mid-levels
looks to result in an increasingly deep layer of steepening
low-level rates Friday afternoon into Friday night. This will
likely support some additional snow showers or even snow
squalls as winds ramp up in response to deepening surface low
pressure over the northern Lakes. Models remain in good
agreement in depicting a reinforcing push of much colder air
arriving later Friday night.

As noted above, the upper level trough is then forecast to
linger across the region through the weekend and into early next
week. Ensembles depict several additional digging short waves
which may bring some additional snow/snow shower chances during
the period, though model spread in the timing and track of
these remains and lowers confidence in adding forecast detail
with respect to these at this time. There is good agreement
however that the push of colder arctic air that arrives Friday
night will persist through the remainder of the period.
Nighttime lows in the single digits and daytime highs in the
upper teens to near 20 appear in store through the weekend and
into early next week. Wind chills look to remain in the single
digits either side of zero, along with occasional chances of
additional snow showers and flurries.

Ratzer

&&

.AVIATION /12Z TAFS THROUGH 18Z THURSDAY/...
Issued at 538 AM CST Wed Jan 14 2026

Aviation forecast concerns for the 12Z TAFs:

- Gusty snow showers this morning, with brief LIFR vis and NNW
  wind gusts around 35 kt possible. Accums around a half inch
  likely.

- North-northwest winds remain strong and gusty through the day,
  only gradually diminishing below 30 kts by early this evening.

A robust mid-level disturbance, accompanied at the surface by a
strong cold front, will bring a period of gusty snow showers to
the terminals early this morning. The front was just pushing
south across the IL/WI border as of 1130Z, with regional radars
depicting a pretty solid band of snow/snow showers across far
south/southeast WI which will move across the terminals over
the next few hours. Surface obs across central/eastern WI have
indicated localized visibilities as low as 1/2-3/4SM within this
band, along with north-northwest winds gusting to around 35
kts. These type of conditions are expected to impact the
terminals through mid-morning or so, before snow showers taper
off to flurries. RFD will likely see a shorter duration of
IFR/LIFR snow showers than the Chicago metro sites.

In the wake of the snow showers, it will remain blustery with
north-northwest winds continuing to gust around 30 kts through
the day while only slowly diminishing into tonight. Lingering
non-impactful flurries are likely from a high MVFR/low VFR
stratocu deck through early evening. Some decrease in cloud
cover is likely toward Thursday morning, as winds continue to
slowly diminish and turn more northwest.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...Winter Weather Advisory until 9 AM CST Thursday for INZ002.

LM...Gale Warning until 9 PM CST this evening for Winthrop Harbor
     IL to Gary IN.

     Gale Warning until 3 AM CST Thursday for Gary to Burns Harbor
     IN-Burns Harbor to Michigan City IN.

&&

$$

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